$ cat a.c
#ifndef __linux__
#error "__linux__ does not exist"
#endif
void a(void)
{
}
$ for i in arm-eabi arm-linux-gnueabi arm-none-linux-gnueabi; do gcc=$i-gcc; $gcc --version; $gcc -c -o ~/tmp/a.o a.c; done
arm-eabi-gcc (GCC) 4.4.3
Copyright (C) 2009 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

a.c:2:2: error: #error "__linux__ does not exist"
arm-linux-gnueabi-gcc (Ubuntu/Linaro 4.6.3-1ubuntu5) 4.6.3
Copyright (C) 2011 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

arm-none-linux-gnueabi-gcc (Sourcery G++ Lite 2010q1-202) 4.4.1
Copyright (C) 2009 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.